A vote will be held tonight at around 7pm after an all-day debate starting after Prime Minister's Questions.

Mr Corbyn will hope it will be the first successful no confidence motion against a government for 40 years - when Margaret Thatcher toppled the Labour government in 1979.

If he is successful it will trigger a two-week countdown to a general election campaign - with an election as early as March 7.

Mr Corbyn said the confidence vote would allow the Commons to "give its verdict on the sheer incompetence of this Government".

But in a major blow, the DUP indicated they would not back him - leaving the vote with little chance of success.

Leader Arlene Foster said: "We will work with the Government constructively to achieve a better deal. That is our focus. Whilst some may wish to use this defeat to boost their political ambitions, we will give the Government the space to set out a plan to secure a better deal."

Labour's leader can table unlimited no confidence votes in the government if the first is not successful.

Shadow Justice Secretary Richard Burgon told BBC News: "If we don't win this no confidence vote this time, then we can bring it again and again and again if necessary."

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We could have a snap general election

A general election is triggered automatically if no party can win the Commons' confidence within two weeks.

That could throw us into a campaign and vote on March 7 at the earliest - just weeks before we leave the EU.

A new government would open up a whole new flowchart of possibilities, which we won't get into properly here.

If Labour takes power, Jeremy Corbyn says he wants to renegotiate a better deal with the EU - which would require delaying the March 29 date of Brexit.

However, he could be 'out-voted' on that policy - because Labour's election manifesto will be finalised by committee once an election is called.

That means, somewhat oddly, that Labour doesn't actually have a firm Brexit policy yet for the general election it's trying to call.

MPs will try to seize control - and block a No Deal Brexit

(Image: PA)

Pretty much the only thing MPs agree on is they don't want a No Deal Brexit.

So expect them to pull out every trick (and amendment) in the book to try and block it in Parliament.

No Deal is the default option, written into law.

But Downing Street claim MPs could effectively seize control of the Commons, by upturning the age-old precedent that the government decides what is debated on what day.

If that decision is passed to MPs, it opens up a whole wealth of possible changes to Brexit - and allows MPs to put forward a Plan B without government permission (see below).

It already looks like it could be going that way. MPs won an amendment that will force the government to seek approval for No Deal spending, one of two defeats to the government the week before the vote.

Pro-EU Tories led by Nick Boles have also tabled a plan that would allow Parliament's 'supergroup', the Liaison Committee, to take charge if the nation is left rudderless.

But committee chief Sarah Wollaston has complained that the liaison committee was not consulted by the plan and No 10 has warned against it.

MPs could put forward their own Plan B...

(Image: Getty Images)

If Theresa May faces undeniable pressure from within, or MPs, or there's a new leader, there could be a new option for Brexit.

Ones that have been mentioned include the much-discussed Norway option, staying in the European Economic Area or EFTA.

Remainers are largely in favour but Brexiteers say it would tie our hands and keep us bound to the EU.

It would also prevent the UK halting free movement.

... And Remain MPs will push for a second EU referendum

(Image: Guy Bell/REX/Shutterstock)

Remain-backers have already been pushing for a second EU referendum, and those calls will only grow.

There is no majority for it in the House of Commons yet.

But Jeremy Corbyn is facing pressure to back it from more of his members in the Labour Party.

He has promised to leave it as an "option on the table" - in his view, a last resort - if the deal is voted down.

But reports suggested 100 Labour MPs would pivot to back a 'People's Vote' and demand their leader follows suit.

The exact path to a second referendum isn't clear. And most say it couldn't be arranged in time before March 29.

The date of Brexit could be delayed - or cancelled

The Article 50 letter

Britain could extend the 29 March date of Brexit - if the EU agrees to as well.

There would need to be a concrete reason to do this, and it'd probably be a short extension.

Also, the EU is holding its Parliamentary elections at the end of May, which would get in the way - badly.

Alternatively, Brexit can be cancelled without the EU's permission by revoking our notification to leave under Article 50 of the Lisbon Treaty.

But while this is legally possible, don't expect it to happen under a Tory government any time soon.

Ex-PM Sir John Major has urged Britain to do this in order to provide the time for a second referendum on EU membership.

Theresa May could resign - and force a Tory leadership race

(Image: REUTERS)

She can't be challenged internally as Tory leader again until December 2019, because she won a no confidence vote and got a year's grace.

But Theresa May could, in theory, be forced to quit by the "men in grey suits" of her Cabinet.

A day before the vote, Downing Street refused to rule out Mrs May quitting if there's a very heavy defeat.

That would spark a Conservative Party leadership contest.

In this case, a new leader would take perhaps a month or two to choose.

First MPs would narrow the candidates down to two; then the 100,000 or so Tory members would vote between the final picks.

The winner would become Prime Minister, without needing to call a general election, and could take Brexit in a dramatically different direction.